Electrical boxes are commonly mounted on ceilings for the purpose of supporting ceiling fans, light fixtures, or other electrical devices. The electrical box provides a safe enclosure to house all wiring connections. Typically, these electrical boxes are secured to the ceiling by a supporting device that spans between two adjacent ceiling joists.
Various considerations are necessary in providing supporting devices for ceiling-mounted electrical boxes. The National Electrical Code specifies a maximum weight of 80 pounds for ceiling light fixtures and a maximum weight of 70 pounds for ceiling fans. It is therefore very important that an installer use adequate load-bearing fasteners for securing the supporting device to the overhead joists. It is also important that the load be carried by the supporting device, and not by the electrical box.
A second consideration arises from the awkwardness of working overhead. Typically, when securing a supporting device and an electrical box to the overhead structure of the ceiling, several separate items must be manipulated. These include the mounting bar, the electrical box, the fasteners for securing the mounting bar to the ceiling structure, and the fasteners for mounting the electrical box to the mounting bar. Considering that the installer is typically on a ladder, this creates a challenging task for any installer. It is therefore imperative that all parts necessary for a successful installation are on hand for the installer.
A third consideration is that the support device must be matched to an electrical box. Many supporting devices are meant to accommodate most commercial electrical boxes. This typically requires complex arrangements on the supporting device to accommodate a variety of boxes.
A further consideration arises as a result of the various different types of ceilings, each of a different thickness. It should be easy for an installer to mount the support device correctly on the overhead joists to position the bottom of the electrical box flush with the ceiling, regardless of the thickness of the ceiling.
Many supporting devices for ceiling fans and fixtures include an arrangement to temporarily secure the device to the ceiling joists including U.S. Pat. No. 5,934,631 to Becker, et al., U.S. Pat. No. 5,954,304 to Jorgensen, U.S. Pat. No. 5,938,157 to Reiker, and U.S. Pat. No. 6,098,945 to Korcz, and U.S. Pat. No. 6,332,597 to Korcz et al.
Although all of the above supporting devices include an arrangement for temporarily fastening the supporting device to overhead joists to free up an installer's hands, they are still not completely satisfactory for simplifying the remainder of the task for installing the electrical box and the light fixture or fan to the supporting device.